Comprehensive profiling of freshwater microalgae from southeastern Bangladesh: Morphological, molecular, and nutritional insights

Microalgae are natural producers of essential nutrients and pigments for both human and animal nutrition as well as medical applications. This study aimed to characterize some microalgae by their taxonomy and biochemical composition. Molecular techniques were used to categorize the microalgal strains into the genera of Chlorococcum, Coccomyxa, and Ochromonas. Subsequently, microalgal growth under laboratory conditions was assessed and the microalgal cells were harvested to determine the pigments, proximate composition, fatty acid, and amino acid profiles. The findings indicated that the cell densities of Coccomyxa sp. and Ochromonas sp. were nearly identical. Additionally, all microalgae exhibited chlorophyll a as the main pigment component, whereas Coccomyxa sp. and Chlorococcum sp. showed significantly highest (p < 0.05) chlorophyll a (7.79 ± 0.07 μg · mL^-1) and chlorophyll b (2.74 ± 0.002 μg · mL^-1), respectively. Significantly higher (p < 0.05) carotenoid and total phycobiliproteins content were found in Ochromonas sp. Furthermore, Coccomyxa sp. was determined to have significantly higher (p < 0.05) protein (31.9% ± 0.46% dry weight) and lipid content (18.2% ± 1.34% dry weight), while the maximum carbohydrate was detected for Ochromonas sp. (29.2% ± 0.1% dry weight). Lastly, essential amino acid (EAA) levels were considerably higher (p < 0.05) in Chlorococcum sp.; however, Coccomyxa sp. produced more polyunsaturated fatty acids (PUFA) in comparison to the other experimental species. The results indicate that the investigated microalgae possess immense potential as multi-nutrient sources and can be optimized for sustainable application in aquaculture, pharmaceuticals, and nutraceutical industries.